PROJECT SUMMARY In our work with patients with neurological disorders, we often encounter patients and families who are afraid. They are afraid that due to their neurodegenerative disorder or potential treatment, such as neurosurgery, they will cease to exist ? they will no longer be who they ?are?. Clinicians typically refer to this construct as personality or characteristic patterns of thinking, feeling, and behaving. Controversy and uncertainty exist regarding the nature and extent of personality changes following deep brain stimulation (DBS) for the treatment of Parkinson's disease (PD). The proposed study systematically explores patients' and care partners' (e.g., family members, friends) perspectives and experiences regarding the preservation of their individually elicited most valued personality characteristics at different stages of PD and over the course of DBS. These narrative lay understandings of personality arising from the participants' lived historical experiences (which may not conform to any existing theories) are highly individualized and value laden. Systematic study of the patients' and care partners' experiences of changes in their most valued personality characteristics is ethically imperative and central to informed consent. The proposed study will employ a mixed methodology incorporating qualitative and quantitative analyses of three groups of 50 patients with PD and their care partners (patients within one year of diagnosis, within 5 -7 years of diagnosis, and those undergoing DBS). Semi-structured interviews will be conducted to identify the core personality characteristics patients and care partners most fear losing (e.g., extroversion, humility). These data will be supplemented with visual analogue scales derived from the qualitative data as well as standard personality and PD-specific metrics. The data from the proposed study will illuminate participant's most valued personality characteristics, identify if existing measure capture those characteristics, illustrate if PD results in changes in perceived personality, demonstrate the concordance between patients' and care partners' ratings of perceived personality change, and confirm if DBS results in changes in individually meaningful personality characteristics. These data have profound implications for the identification/development of measures that mirror patients' values; will contribute to a novel iterative informed consent process that includes systematic assessment of patient's values, goals and perceived personality changes; will inform philosophical and public discussions of identity and autonomy in the context of DBS; and, most importantly, may allow clinicians to ease needless fears.